The initial one was more about video. Although, he covered PCM audio quite a bit, and it was enough that the majority of the questions were about the audio portion of the video. So this second one is to answer a lot of those questions.

I don't usually go in for fancy DACs, but do look at the analog components that sit before an ADC, or after the DAC. While most have specs that out perform human perception by so much it's ridiculous, there are some with pretty serious design flaws that cause strange interactions with what they're connected to. This is especially true when driving headphones. Also with ADCs its important that their decimation filter remove all content above the Nyquist limit, or that limit be raised by running at a higher sampling rate.